A Phase 4 interventional study of Doxycycline hyclate delayed released 200 mg and Doxycycline hyclate delayed released 200 mg weekly in Gonorrhea, Chlamydia and Syphilis, sponsored by Westat. Recruiting at 13 sites in United States. Open to female participants aged 13 Years to 29 Years. Per ClinicalTrials.gov, last updated 2026-10-16.
Sponsored by Westat · Phase 4, Interventional, and Prevention
The goal of this open-label, randomized trial is to assess the efficacy of doxycycline prophylaxis in reducing incidences of bacterial sexually transmitted infections (STIs) among adolescent and young adult females while also evaluating acceptability and antimicrobial resistance in order to inform public health policy.
Participants will be randomized to receive on-demand doxycycline post-exposure prophylaxis (doxyPEP), weekly doxycycline, or standard of care (SOC) and will be followed quarterly to assess the impact of doxycycline use on the quarterly incidence of STIs (gonorrhea [GC], chlamydia [CT], and early syphilis), and within the doxycycline arms adherence and acceptability of weekly versus on-demand dosing.
Approximately 760 females will be randomized 1:1:1 to (1) on-demand doxyPEP (doxycycline 200 mg as soon as possible and within 72 hours after any condomless oral, vaginal, and/or anal sex), (2) weekly doxycycline (doxycycline 200 mg weekly regardless of sexual activity), or (3) SOC (quarterly STI testing/treatment and sexual health counseling). Participants will complete quarterly study visits over the course of 1 year during which they will receive STI testing (GC, CT, and syphilis), complete surveys, undergo safety monitoring, provide specimens for objective markers of doxycycline adherence and other laboratory assessments, and provide specimens (vaginal and rectal swabs [participant self-collected or staff-collected if the participant prefers]) for future testing, such as microbiome analysis. Resistance testing will be conducted on Staphylococcus (S.) aureus and Neisseria (N.) gonorrhoeae isolates to evaluate for doxycycline and tetracycline resistance, respectively. Participants will also complete weekly assessments of sexual activity and doxycycline adherence via the HealthMpowerment (HMP) application (app).
167 studies on the registry are indexed under Gonorrhea; 31 are open to participants now.
This study's planned enrollment of 760 is above the median of 400 across 125 interventional studies indexed under Gonorrhea.
Browse Gonorrhea studies →Westat is the lead sponsor of 23 studies on the registry; 6 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will take by mouth doxycycline 200 mg as soon as possible and within 72 hours after any condomless oral, vaginal, and/or anal sex in addition to standard of care STI testing/treatment and sexual health counseling.
Drug: Doxycycline hyclate delayed released 200 mg
Participants will take by mouth doxycycline 200 mg weekly regardless of sexual activity in addition to standard of care STI testing/treatment and sexual health counseling.
Drug: Doxycycline hyclate delayed released 200 mg weekly
Participants will be followed per standard of care with quarterly STI testing/treatment and sexual health counseling.
Other: Per standard of care with quarterly STI testing/treatment and sexual health counseling
200 mg of doxycycline taken by mouth as soon as possible and within 72 hours after any condomless oral, vaginal, and/or anal sex along with STI screening and sexual health counseling
200 mg of doxycycline taken by mouth weekly regardless of sexual activity along with STI screening and sexual health counseling
Quarterly STI testing/treatment and sexual health counseling
Combined incidence of GC, CT, and/or early syphilis infection
Overall combined incidence of GC, CT, and/or early syphilis infection by laboratory-based diagnosis (defined as positive GC or CT on nucleic acid amplification test \[NAAT\] or first positive rapid plasma reagin \[RPR\] with positive treponemal-specific antibody \[Ab\] or a new 4-fold rise in RPR titers) over the duration of follow-up.
Time frame: One (1) year
Individual incidence diagnoses of GC, CT, and early syphilis infection
Individual incidence diagnoses of GC, CT, and early syphilis infection by laboratory-based diagnosis (defined as positive GC or CT on NAAT or first positive RPR with positive treponemal-specific Ab or a new 4-fold rise in RPR titers) per quarter, by arm.
Time frame: One (1) year
First occurrence of a bacterial STI
First occurrence of a bacterial STI (GC, CT, and/or early syphilis) after study enrollment, based on testing during each quarterly follow-up visit or documented testing occurring at an outside clinical site, by arm.
Time frame: One (1) year
Proportion GC isolates that are detected as tetracycline-resistant
Proportion of GC isolates that are detected as tetracycline-resistant during follow-up, by arm.
Time frame: One (1) year
Proportion S. aureus isolates that are detected as doxycycline-resistant
Proportion of S. aureus isolates that are detected as doxycycline-resistant at 24 and 48 weeks, by arm.
Time frame: One (1) year
Adherence to doxycycline
Adherence to on-demand doxyPEP and weekly doxycycline assessed with objective doxycycline plasma, and/or DBS concentrations matched with expected detection of once-weekly dosing or based on self-reported sexual behavior, by arm.
Time frame: One (1) year
Adherence to doxycycline - self report
Adherence to on-demand doxyPEP and weekly doxycycline assessed with self- reported proportion of sexual exposures within the prior 12 weeks when on-demand doxyPEP and weekly doxycycline was used, by arm.
Time frame: 1 year
Acceptability and optimism
Acceptability and optimism, using Likert scales, by arm.
Time frame: One (1) year
Plan to share: No
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From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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